Apparatus for controlling oil wells



June 22, 1943. H. KAVELE 2,322,453

' APPARATUS FOR CONTROLLING OIL WELLS Filed Sept. '23, 1940 2Sheets-Sheet 1 SEPARATOR GAS SPECIFIC GRAVITY INVENTOR H. H. KAVELER BYM, n

7 ATI'O NEY June 22, 1943. H, H. KAVELER 2,322,453

APPARATUS FOR CONTROLLING OIL WELLS Filed Sept. 25, 1940 2 Sheets-Sheet2 GAS SPECIFIC GAS SPECIFIC GRAVITY BALANCE INVENTOR H.H. KAVELER RNEYPatented June 22, 1943 2,322,453 APPARATUS Fon. CONTROLLING on. WELLSHerman fle liaveler, Bartlesville, kla., assignor to'lhillips PetroleumCompany, a corporation of Delaware npplicatlon'september'zii,1940;581'13110. 357,998

8 Claims.

This invention relates to apparatus for controlling the withdrawal offluid through a well bore; and is a continuation in part of my priorfiled application, Serial No, 276,108, filed May 2'7, 1939.

The gas production from an oil well is conveniently expressed inrelation to the oil production by the so-called gas-oil ratio. Thegasoil ratio is generally defined as the ratio of the number of cubicfeet of separator gas measured at 60 F. and some reference pressure(usually 14.4 pounds, absolute) to the number of barrels of oilproduced, measured at 60 F. and prevailing atmospheric pressure. Theratio therefore expresses the number of cubic feet of gas producedper'barrel of oil during some period of fiow.

Heretofore, the only method for accurately determining gas-oil ratioswas to measure separately the oil produced in a stock tank and the gasproduced through a separator vent-line having an orifice meter or Pitottube in place. This method of gauging separately the oil and gasproduced shall be referred to as the direct method of determining theratio. This method requires that a separator and storage tank beprovided for each well under test during the test period which usuallyextends from one to. twenty-four hours.

The gas-oil ratio of an oil well is dependent on a number of factorssuch as:

1. Inherent reservoir properties as established by reservoir rock,reservoir temperature and pressure and chemical composition of thereservoir contents,

2. The presence in the reservoir of a free gas phase commonly referredto as a gas-cap,

3. The manner in which wells are completed and the method of producingthe well (flow rate, choke size, etc.), and

4. The state of depletion of the reservoir.

Gas is the principal source of natural energy available for theproduction of oil and every eflort is made to conserve reservoir gas byproducing oil wells in such a way as to maintain the minimum gas-oilratio since gas-oil ratios are important in establishing conservativeoperation of oil reservoirs. Regulatory bodies frequently requireextensive periodic gas-oil ratio tests to provide a basis for enforcingthe laws established for conservation purposes. I

The determination of gas-oil ratios by the direct method described aboveis time consuming and often expensive whenever individual separators andstock tanks are required for each well under test. This situation led toa search for som other method of accurately determining gas-oil ratioswhich would permit a saving of time in observation and which wouldsimplify the mechanical equipment required for individual well tests.

In searching for other means of determining gas-oil ratios, a simplerelationship between gasoil ratio and th specific gravity of the gasproduced with the oil has been discovered. The employment of thisrelationship in actual practice provides a means of indirectlydetermining gasoil ratios to an accuracy of 10 to 15 per cent.

It is an object of the present invention to effectively control thewithdrawal of fluid through a well bore.

Another object of the invention resides in the utilization of thespecific gravity of produced gas in the regulation of the gas-oil ratioof fluid withdrawn through a well bore that communicates with anoil-bearing formation.

A further object of my invention is the provision of apparatus forregulating the fiow of hydrocarbons through a Well bore to maintain thegas-oil ratio thereof within preselected limits. Other objects andadvantages of the invention will be apparent during the course of thefollowing description.

In the accompanying drawings, forming a part of this specification, andin which like numerals are employed to designate like parts throughoutthe same, T l

Figure 1 shows a schematic diagram of the surface equipment to be usedin determining gas gravities, and

Figure 2 is a graph showing the relation between gas-oil ratio andspecific gravity of separator gas.

Figure 3 is a schematic diagram of one appli cation of my invention.

Figure 4 is a schematic diagram of another application of my invention.

Figure 5 illustrates a form of gas specific gravity balance, partly incross section, that may be advantageously employed in the practice ofthis invention.

An example of the relationship between gasoil ratio and the specificgravity of gas produced with the oil is given in the following datawhich were obtained from field observations in which the gas-oil ratiowas determined by direct observation.

Example of the relation between gas-oil ratio and the specific gravityof produced gas Separator pressure30 pounds per square inch gauge Thesedata are represented in Figure 2 which we shall call a gravity-ratio"curve. Each and every producing horizon in any field can be representedby a typical "gravity-ratio curve, such as that cited in the exampleabove. Such representative curves must be established by a field testusing the direct method of measuring ratio or the curves may beestablished by computations if the hydrocarbon analyses of the reservoirliquid and gas and proper equilibrium constants are available. Thelatter involves operations already known and accepted in petroleumtechnology.

The gas-oil ratio as defined above depends upon separator pressure sincethe amount of gas dissolved in the separator liquid and the specificgravity of the produced gas may change sensibly with pressure. Thegravity-ratio curve must be determined and interpreted always withrespect to a chosen, arbitrary separator prwsure. Further, in caseswhere the separator temperature shows variations in excess of 20 F., acalibration curve to establish the temperature correction would benecessary. In nearly all cases, however, the temperature will not be animportant variable. The gravity-ratio curve for a given horizon in agiven field will depend upon the pressure in the producing horizon insuch a manner that the gravity-ratio curve cited above may have to beredetermined at such intervals as declining reservoir pressures requirethe adjustment of the curve.

Having the gravity-ratio curve established for a particular field in themanner described above,

, it is only necessary to observe the specific gravity of the producedgas to obtain the gas-oil ratio. This observation can be made on gasproduced from the separator or, to make the greatest use of thediscoveredrelation, the observation may be made directly in the flowline. All that is required is a means of withdrawing samples of theproduced gas into a gas specific gravity meter.

Figure 1 shows a current means of doing this through either nipples 4and 5, which are approximately 2 by 12 inches, attached to the uppersideof the'flow line 3 through which representative samples of theproduced gas could be withdrawn. In' the drawings, I represents aproducing well, and 2, a flow control valve mounted on top of the.casing of the well. The fiow line 3 connects into the oil-gas separator6 and delivers the fluid from the well thereto. Valve I is a fioat valvearrangement which controls valve 8 in flow line 9 to allow for dischargeof oil from the .oil-gas separator. Line In running from the top of theoil-gas separator is the vent line conducting the gas from theseparator. The nipple I i represents another point at which samples ofthe gas may be taken to be run through the specific gravity meter. Thevalve I2 is a pressure regulator which determines the pressure underwhich the separator 6 operates. Should the pressure in separator 8 andline Ill exceed a predetermined pressure. for example,

. within separator 6 is reduced to below this predetermined pressure,regulator valve l2 automatically operates again to terminate the ventingof gas. An additional nipple l3, through which samples of the gas may bewithdrawn, is indicated on the down stream side of pressure regulatorl2.

As can be seen from the drawings, the position of the sampling nipplescan be: (1) In the separator vent line ID as at H and I3 or (2) In theflow line 3 to the separator as at 4 and 5. The nipples 4 and 5 shouldbe located near the separator in order that the pressure at the nipplemay be responsive to separator regulation. The location of the samplingnipples 4 and '5 permits observation of gas-oil ratios without thenecessity of individual separator and stock tank installations, andfurthermore, this is the only method heretofore proposed which permitsgasoil ratios to be determined in the flow line before v the gas and oilphases are separated.

' Besides the simplified means of determining gas-oil ratios fromobservation of the. specific gravity of gas produced in either vent orfiowerator may manually adjust the control valve on the well to suchpositions as give the maximum gravity of the produced gas (for a chosenseparator pressure) and maintain, therefore, the desirable minimumgas-oil ratio. In the other instance when the well is artesian, thespecific gravity meter may be installed with auxiliary equipment whichwill operate the surface control valves automatically. The inventionalso provides the means for automatically controlling variablesubsurface chokes in artesian wells. Furthermore, my instant inventioncontemplates operating variable speed pumps of all types in such amanner as to provide automatic adjustments to maintain optimum gas-oilratios.

My invention may be employed to control the operation of a variablespeed pump and an embodiment of such an application of the invention isset forth in Figure 3 of the drawings, wherein a conduit l4,'conn'ectedto nipple 4, transmits produced gas to a gas specific gravity balanceI5, which is provided with-a gasvent I6. It is to be understood thatconduit It may be connected to nipples 5, l| or 13, if desired, withequally satisfactory results. The gas gravity meters specific gravitybalance is or a conventional type, the particular constructionillustrated in Figure including a case I! within which is a fulcrum.

l8 supporting a balance arm l8 having a spherical bulb 28 at one end andan adjustable counterbalance contact member 2! at its opposite end.Above and below contact member 2| is a pair of electrical contacts 22and 23 which are both connected to a common electric lead 24 while armI9 is connected to a similar lead 25. The balance may be readilyadjusted so that when the specific gravity of the gas passingtherethrough is above or below a chosen value of specific gravity,electric contact is made between member 2| and contact 22 or 23 tocompletean electric circuit, generally indicated by reference numeral 26(Figure 3). If desired, the balance may be designed to complete theelectric circuit only when the gas specific gravity is less than apredetermined minimum. This may be accomplished by merely eliminatingcontact 22 from the balance. The electric circuit includes a source ofelectrical energy, such as the plurality of batteries 21 shown in thedrawings, a timing device 28 and a power relay 29,

all arranged in series. A pair of electric leads 30 connects the powerrelay to an electric solenoid having a casing 3|. This solenoid actuatesa plunger 32 passing therethrough. A coil spring 33 interposed betweenplunger 32 and a rigid bail 34 normally maintains the plunger in aretracted position when the solenoid is deenergized. 'Should thespecific gravity of the gas passing through balance I5 b above or belowthe chosen value, electrical contact is made within the balancecompleting circuit 26, thereby placing power relay 29 into service andenergizing solenoid 3|. Plunger 32 is urged downwardly into a valve 35in gas line 36 to partially or completely cut oil the flow of gasthrough this line. This regulation of the amount of gas passing throughline 36 will in turn determine the speed at which various types of pumps31, such as gas lift pumps of the type set forth in U. S. Patent2,142,482, or 2,142,485, will operate. Pump 31 will be completely closeddown, or operate at reduced speed as long as solenoid 3| is energized.

The circuit may be interrupted at any desired time by means of timingdevice 28, which is automatically placed in service when circuit 26 iscompleted and continues to operate for a predetermined period of time.At the end of such period, timing device 28 is designed to break theelectrical circuit, thereby allowing plunger 32 to be retracted byspring 33 and reopen valve 35 to allow unrestricted flow of gas throughline 36 and to pump 31.

Figure 4 illustrates a form of my invention which is adaptable tocontrol flowing wells by operating a variable choke that is associatedwith the well. It will be noted on inspection of the apparatus depictedin Figure 4 that substantially the same equipment is utilized in thisembodiment of my invention as that illustrated in Figure 3. In thisparticular instance, the gas specific gravity balance l5 cooperates withthe various items of electrical equipment to control the degree ofopening of a variable choke 38.

While I have thus illustrated and described several embodiments coveringthe application of my invention, it will be obvious that my inventionlends itself to a number of other uses taken as the preferred example ofthe same, and that various changes in the shape, size and arrangement ofparts may be resorted to, without departing from the spirit of myinvention, or the scope of the subjoined claims.

I claim:

1. Apparatus for controlling the withdrawal of fluid including g s andoil through a well bore comprisingmeans associated with the well and"actuable by variations in the specific gravity of said gas, and meansresponsive to actuations of said means for controlling the flow oi wellfluid whereby the gas-oil ratio of fluid withdrawn from the well is notpermitted to exceed a predetermined maximum.

2. Apparatus for controlling the withdrawal of fluid including gas andoil through a well bore comprising a gas specific gravity balanceoperating between chosen limits or specific gravity of said gas, andmeans associated with the balance and cooperating therewith forcontrolling the flow of well fluid at predetermined gravities of the gaswhereby the gas-oil ratio of fluid withdrawn from the well is maintainedwithin a chosen range.

3. Apparatus for controlling the withdrawal or fluid including gas andoil through a well bore comprising means associated with the well andactuable by variations in the specific gravity of said gas, andelectrical means responsive to actuations of said means for controllingthe flow of well fluid whereby the gas-oil ratio of fluid withdrawn fromthe well is not permitted to exceed a predetermined maximum.

4. Apparatus for controlling the withdrawal of fluid including gas andoil through a well bore comprising a gas specific gravity balanceoperating between chosen limits of specific gravity of said gas, andelectrical means associated with the balance and cooperating therewithfor controlling the flow of well fluid at predetermined gravities of thegas whereby the gas-oil ratio of fluidwithdrawn from the well ismaintained within a chosen range.

5. In apparatus for controlling the withdrawal of fluid from an oilwell, the combination comprising a gas specific gravity balance, meansintermediate the well and the balance for transmitting gas from the wellto the balance, a variable speed pump in the well, and means cooperatingwith the balance and the pump to control the speed of the pump toproduce the well at predetermined gravities of said gas whereby thegasoil ratio of fluid withdrawn from the Well is not permitted to exceeda predetermined maximum.

6. In apparatus for controlling the withdrawal or fluid from an oilwell, the combination comprising a gas specific gravity balanceoperating between chosen limits of specific gravity of gas admittedthereto, means intermediate the well and the balance for transmittinggas from the well to the balance, a variable speed pump in the well, andmeans cooperating with the balance and the pump to control the speed ofthe pump to produce the well at predetermined gravities of said gaswhereby the gas-oil ratio of the fluid withdrawn from the well ismaintained within achosen range.

'7. In apparatus for controlling the flow of an oil well, thecombination comprising a gas specific gravity balance, meansintermediate the well and the balance for transmitting gas from the wellto the balance, a variable choke associated with the well, and meanscooperating with the balance and the choke to actuate the choke to flowthe well at predetermined gravities of said gas whereby the gas-oilratio of fluid withdrawn from the well is not permitted to exceed apredetermined maximum.

8. In apparatus for controlling the flow of an oil well, the combinationcomprising a gas specific gravity balance operating between chosenlimits or specific gravity of gas admitted thereto, means intermediatethe well and the balance for transmitting gas from the well to thebalance, a variable choke associated with the well, and meanscooperating withthe balance and the choke to actuate the choke to flowthe well at predetermined gravities of said gas whereby the gas-oilratio of fluid withdrawn from the well is maintained within a chosenrange. a v

HERMAN H; mvmm.

